In recent years, there has been a strong demand for reduction in effluent resulting from the wet processing of image forming materials in the field of medicine and in the manufacture of printing plates, in view of protecting the environment and conserving space.
Accordingly, there is need for techniques relating to photothermographic materials for use in photography technology in which effective exposure such as that of a laser imager or laser image setter is possible, and in which clear black and white images with high resolution can be formed.
Known examples of techniques for the photothermographic dry imaging material include silver salt photothermographic dry imaging materials including an organic silver salt, light-sensitive silver halide and a reducing agent on a support (for example Patent Documents 1 and 2, Non-Patent. Document 1). The silver salt photothermographic dry imaging material is advantageous in that the user is provided with a system that is simpler and which does not damage the environment because processing chemicals in solution-form are never used.
These silver salt photothermographic dry imaging materials are characterized by the fact that the light-sensitive silver halide grains which are provided in a light-sensitive layer are used as a photo-sensor and the organic silver salt is the supply source for silver ions, such that images are formed by thermal development commonly at 80-140° C. using the reducing agent which is incorporated, and fixing need not be performed.
However, after exposure, because only thermal development is carried out commonly at 80-250° C. and fixing is not performed, some or all of the silver halide, the organic silver salt and the reducing agent remain after thermal development.
Thus, during extended storage, there is the problem that image quality such as silver image tone and the like tends to vary due to the fact that metallic silver is created by heat and light.
Occurrence of this type of phenomenon is remarkable in the case where the laser imager is made compact. It is thought that the reason for this is the cooling section becomes relatively small due to the smaller size and the cooling efficiency is reduced.
It is thought that when the cooling efficiency is reduced, the imaging material is discharged while it is still in an active state.
Techniques for shortening the length of the cooling section in order to make the laser imager compact have been disclosed (for example in Patent Document 3). However the imaging material is light-sensitive even after being subjected to the cooling process and in the case where the ratio of the length of the thermal development section and the cooling section is not more than 1.5 and therefore short, the above-described problem with respect to storage occurs and significant improvement is being demanded.
[Patent Document 1] U.S. Pat. No. 3,152,904 specification (Scope of the Claims)
[Patent Document 2] U.S. Pat. No. 3,487,075 specification (Scope of the Claims)
[Non-Patent Document 1] D. Morgan, B. Shelly; Thermally Processed Silver Systems A; Imaging Processes and Materials: Neblette Eighth edition, Editors: Sturge, V. Walworth, A. Shepp Page 2, 1989
[Patent Document 3] Japanese Patent Application Laid-Open No. 2004-4522 publication (Scope of the Claims)
The present invention was conceived in view of the foregoing situation and the object thereof is to provide a processing method and thermal development device for a photothermographic dry imaging material which is capable of providing images with high diagnostic characteristics even if the conveyance path in the cooling section is short due to the cooling section being made relatively small due to compacting of the device.